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Ultrahot giant exoplanets receive thousands of times Earth’s insolation1,2. Their high-temperature atmospheres (greater than 2,000 kelvin) are ideal laboratories for studying extreme planetary climates and chemistry3–5. Daysides are predicted to be cloud-free, dominated by atomic species6and much hotter than nightsides5,7,8. Atoms are expected to recombine into molecules over the nightside9, resulting in different day and night chemistries. Although metallic elements and a large temperature contrast have been observed10–14, no chemical gradient has been measured across the surface of such an exoplanet. Different atmospheric chemistry between the day-to-night (‘evening’) and night-to-day (‘morning’) terminators could, however, be revealed as an asymmetric absorption signature during transit4,7,15. Here we report the detection of an asymmetric atmospheric signature in the ultrahot exoplanet WASP-76b. We spectrally and temporally resolve this signature using a combination of high-dispersion spectroscopy with a large photon-collecting area. The absorption signal, attributed to neutral iron, is blueshifted by −11 ± 0.7 kilometres per second on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside16. In contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. We conclude that iron must therefore condense during its journey across the nightside.

This paper presents a real-time trip-planner system for the public transport in Lisbon. This system has the capability of informing potential customers about which are the best routes to make the trip they want, when they want and what are the expected travel times, based on the actual locations of the public transport vehicles and the travel speeds that can be estimated for the various relevant road segments for the next hour. Using four months of operation log-files from the bus operator Carris, a process of data mining was created to analyse and classify the information of travel times and speeds. The trip-planner is built upon an agent-based model that aims to simulate the transport network operation and create a model to make short-term travel times forecast. A system of dynamic queries was introduced in order to evaluate the built model. The obtained results indicate that this tool, if deployed, could achieve high accuracy levels in predictions and become very useful and valuable for urban public transport users.

High precision measurements of long distances for intrasatellite ranging have very specific requirements and constraints. In particular, performance parameters like accuracy, ambiguity range, update rate, complexity, weight and flexibility are of great relevance for space missions. The baseline of optical laser metrologies for distance measurement in space relies on diode pumped Nd:YAG NPRO (Non-Planar Ring Oscillator) lasers with significant demands on power, mass, and cost. Semiconductor diode lasers represent one option, offering compactness, integrability and flexibility, but the current drawback of this technology is the non-availability of frequency-stable laser diodes, either CW or pulsed. In this paper we present a new metrology concept based on quantum dot modelocked diode laser with relaxed requirements in terms of frequency stability, that can meet the specifications of a metrology system for intrasatellite distances up to 250m with accuracies better than 100 micrometers.

We combine the available astrometric and photometric data for the 1993 microlensing event MACHO-LMC-5 to measure the mass of the lens, = 0.097 +- 0.016 . This is the most precise direct mass measurement of a single star other than the Sun. In principle, the measurement error could be reduced as low as 10% by improving the trigonometric parallax measurement using, for example, the Space Interferometry Mission. Further improvements might be possible by rereducing the original photometric light curve using image subtraction or by obtaining new, higher precision baseline photometry of the source. We show that the current data strongly limit scenarios in which the lens is a dark (i.e., brown dwarf) companion to the observed M dwarf rather than being the M dwarf itself. These results set the stage for a confrontation between mass estimates of the M dwarf obtained from spectroscopic and photometric measurements and a mass measurement derived directly from the star's gravitational influence. This would be the first such confrontation for any isolated star other than the Sun.

The rotation of the disk of the Large Magellanic Cloud (LMC) is derived from the published radial velocities of 422 carbon stars. New aspects of this analysis include the propagation of uncertainties in the LMC proper motion with a Monte Carlo and a self-consistent modeling of the rotation curve and disk kinematics. The LMC rotation curve reaches a maximum circular velocity of 72 +- 7 km s-1 at R = 4.0 kpc and then declines. The rotation curve is well fitted by a truncated, finite-thickness exponential disk model with no dark halo, implying a total mass of 5.3 +- 1.0 x 109 M. The velocity dispersion in concentric radial bins from R = 0.5 to 5.6 kpc decreases from 22 to 15 km s-1 and then increases to ~20 km s-1 at larger radii. Constant-thickness disk models in virial equilibrium cannot be reconciled with the data even if the effects of LMC or Galactic dark halos are included. If the disk is virialized, the scale height rises from h = 0.3 to 1.6 kpc over the range of R = 0.5-5.6 kpc. Thus, the LMC disk is flared. We model the velocity dispersion at large radii (R > 6 kpc) as a maximal flared disk under the influence of the Galactic dark halo, which favors a mean density for the latter of img1.gif ~ 2.5 x 10-4 M pc-3 at the LMC distance. LMC stellar kinematics plays an important role in elucidating the nature of MACHOs, a dark population inferred from LMC microlensing. We have constructed a truncated and flared maximal disk model for the LMC that is kinematically based. Our model does not include a nonvirialized component such as tidal debris. The instantaneous probability of microlensing from LMC stars in our model is t < 1.0 x 10-8 sec2 i, where i is the disk inclination. Our upper limit on the self-lensing optical depth is in good agreement with that obtained from less sophisticated models and is an order of magnitude too small to account for the MACHO microlensing signal.

The average near-infrared (K-band) luminosity of 238 Hipparcos red clump giants is derived and then used to measure the distance to the Galactic center. These Hipparcos red clump giants have been previously employed as I-band standard candles. The advantage of the K-band is a decreased sensitivity to reddening and perhaps a reduced systematic dependence on metallicity. In order to investigate the latter, and also to refer our calibration to a known metallicity zero point, we restrict our sample of red clump calibrators to those with abundances derived from high-resolution spectroscopic data. The mean metallicity of the sample is [Fe/H] = -0.18 dex (s = 0.17 dex). The data are consistent with no correlation between MK and [Fe/H] and only weakly constrain the slope of this relation. The luminosity function of the sample peaks at MK = -1.61 +- 0.03 mag. Next, we assemble published optical and near-infrared photometry for ~20 red clump giants in a Baade's window field with a mean metallicity of [Fe/H] = -0.17 +- 0.09 dex, which is nearly identical to that of the Hipparcos red clump. Assuming that the average (V-I)0 and (V-K)0 colors of these two red clumps are the same, the extinctions in the Baade's window field are found to be AV = 1.56, AI = 0.87, and AK = 0.15, in agreement with previous estimates. We derive the distance to the Galactic center: (m - M)0 = 14.58 +- 0.11 mag, or R = 8.24 +- 0.42 kpc. The uncertainty in this distance measurement is dominated by the small number of Baade's window red clump giants examined here.

Color-magnitude diagrams of globular clusters usually exhibit a prominent horizontal branch (HB) and may also show features such as the red giant branch (RGB) bump and the asymptotic giant branch (AGB) bump. Stellar evolution theory predicts that the luminosities of these features will depend on the metallicity and age of the cluster. We calculate theoretical lines of 2-12 Gyr constant age RGB bumps and AGB bumps in the DV$\mathstrut{^{{\rm HB}}_{{\rm Bump}}}$-[Fe/H] diagram, which shows the brightness difference between the bump and the HB as a function of metallicity. In order to test the predictions, we identify giant branch bumps in new Hubble Space Telescope color-magnitude diagrams for eight SMC clusters. First, we conclude that the SMC cluster bumps are RGB bumps. The data for clusters younger than ~6 Gyr are in fair agreement with our predictions for the relative age-dependent luminosities of the HB and RGB bump. The DV$\mathstrut{^{{\rm HB}}_{{\rm Bump}}}$ data for clusters older than ~6 Gyr demonstrate a less satisfactory agreement with our calculations. We conclude that ~6 Gyr is the lower bound to the age of clusters for which the Galactic globular cluster, age-independent DV$\mathstrut{^{{\rm HB}}_{{\rm Bump}}}$-[Fe/H] calibration is valid. Application of the DV$\mathstrut{^{{\rm HB}}_{{\rm Bump}}}$-[Fe/H] diagram to stellar population studies is discussed.

In 1993, noncytopathic bovine viral diarrhea virus (BVDV) strains with enhanced virulence caused unprecedented outbreaks of severe acute bovine viral diarrhea (BVD) in dairy, beef, and veal herds in Ontario (Canada). Fever, pneumonia, diarrhea, and sudden death occurred in all age groups of cattle. Abortions often occurred in pregnant animals. Gross lesions in the alimentary tract were similar to those associated with mucosal disease, especially in animals >6 months of age. Cattle of all age groups had microscopic lesions in the alimentary tract similar to those seen with mucosal disease. The epidemic peaked in the summer of 1993, with 15% of all bovine accessions from diseased cattle presented to the diagnostic laboratory being associated with BVDV. The virus strains involved in the outbreak were analyzed using monoclonal and polyclonal antibodies and the polymerase chain reaction. The virus isolates from these outbreaks of severe disease were determined to be type 2 BVDV. Type 2 BVDV has been present in Ontario at least since 1981 without causing widespread outbreaks of severe acute BVD, which suggests that type 2 designation in itself does not imply enhanced virulence. Cattle properly vaccinated with type 1 BVDV vaccines appear to be protected from clinical disease.

OBJECTIVE: To determine the cause of an outbreak of Escherichia coli 0157:H7 related to animal exposures so that further transmission could be prevented.DESIGN: Description of laboratory investigations and a case control study.SETTING: Agricultural pavilion at an annual fair in Ontario.POPULATION: People with laboratory evidence of E coli 0157:H7 (seven people) and others with diarrhea (155 people) who called the health unit following a media release were interviewed. Animals that were accessed most frequently by the public in the agriculture pavilion were tested for E coli 0157:H7. In the case control study, a case was defined as someone with laboratory-confirmed E coli 0157:H7, or someone who developed severe or bloody diarrhea two to eight days after attending the agricultural pavilion at the fair (61 people). A convenience sample of people who attended the agricultural pavilion but did not develop diarrhea was selected as the control group (89 people).INTERVENTIONS: Human and animal E coli 0157:H7 specimens were subtyped. Cases and controls were interviewed using a standardized questionnaire.RESULTS: Subtyping of the seven human isolates of E coli 0157:H7 revealed five that were of an extremely uncommon phage type. Three samples from goats and one from sheep at the petting zoo in the agricultural pavilion were of this same phage type. The case control study also implicated goats (odds ratio [OR] 3.65; 95% CI 1.63 to 8.52) and sheep (OR 2.94; 95% CI 1.33 to 6.57) from the petting zoo.CONCLUSIONS: Results of this investigation suggest strongly that the goats and sheep from the petting zoo were the source of this outbreak of E coli 0157:H7.

Fecal samples from 335 dairy farm residents and 1458 cattle on 80 farms were tested for Vero cytotoxin (VT)–producing Escherichia coli (VTEC). Residents were also tested for antibodies to VT1 and O157 lipopolysaccharide (LPS). Residents and cattle on farms with VTEC-positive persons or E. coli O157:H7–positive cattle were retested. Twenty-one persons (6.3%) on 16 farms (20.8%) and 46% of cattle on 100%of the farms had VTEC in fecal samples. Human VTEC isolates included E. coli O157:H7 and 8 other serotypes, 4 of which were present in cattle on the same farms. More persons had antibodies to VT1 (41%) than to O157 LPS (12.5%). Seropositivity to 0157 LPS was associated with isolation of E. coli O157:H7 on the farm (P = .022). Human VTEC infection was negatively associated with age (P < .05) and was not associated with clinical illness. Many dairy farm residents experience subclinical immunizing VTEC infections at a young age, which frequently involve non-O157 VTEC found in cattle.